SIR systems used in automotive vehicles commonly have a plurality of airbags to provide frontal protection and side protection for both passenger and driver positions. In at least some jurisdictions it is considered to be desirable to offer an option to suppress or disable one or more of the airbags either directly by the vehicle operator or by authorized service personnel. It is desirable to have an indicator viewed by the operator which shows the state of each airbag as well as to have a permanent record of an airbag disabled state in the event of a crash. In addition, the disabling must not interfere with diagnostic processes performed by the crash sensing module, else a fault warning would be displayed where, in fact, there is no fault. Still another requirement is that the permanent record utility should be fully operative with those systems which use precision inflator resistances and with very short deployment current pulses, on the order of 100 .mu.s.
A circuit for meeting some of the above objectives is described in the U.S. Pat. No. 5,544,914 to Borninski et al entitled "AIR BAG DISABLER CONTROL CIRCUIT". There a resistive test load is provided to take the place of the airbag inflator and a switch is operated to select either state. The dummy resistive test load allows a diagnostic operation to take place. A fuse in series with the resistive test load is used to indicate that deployment current has passed through the resistor, thereby indicating that the inflator was disabled when a crash occurred. The properties of such fuses are that they are available only in low precision resistance values so that the series combination of the resistive test load and the fuse cannot have high precision, and a relatively long current duration is needed to operate the fuse. Thus the proposed arrangement has no application to a SIR system which requires high precision test load values or which uses very short current pulses for airbag deployment. High precision test loads are not required where the circuit is specifically designed for a particular model SIR system. However, a suppression controller intended as a retrofit controller for a number of existing SIR products having various firing loop connectors and harnesses is able to operate correctly only when tight tolerances are maintained in the controller design; in that case a precision test load is required.